This disclosure relates generally to an assembly, system and method for generating X-rays. In particular, this disclosure relates to the use of an RF accelerator for generating X-rays and/or for accelerating electrons toward a target for generating X-rays in an imaging apparatus.
X-ray sources such as X-ray tubes generally include a cathode assembly and an anode assembly disposed within a vacuum vessel. The cathode assembly is positioned at some distance from the anode assembly, and a voltage differential is maintained therebetween in order to accelerate the electrons toward the anode. This voltage differential generates an electric field having a strength defined as the voltage differential between the anode and cathode divided by the distance therebetween. The anode assembly includes an anode having a target or impact zone that is generally fabricated from a refractory metal with a high atomic number, such as tungsten or any tungsten alloy. The anode is commonly stationary or a rotating disc. The cathode assembly emits electrons in the form of an electron beam that are accelerated across the potential difference and impact the target track of the anode at a high velocity. As the electrons impact the target, the kinetic energy of the electrons is converted to high-energy electromagnetic radiation, or X-rays. A portion of the X-rays are directed out of an X-ray transmissive window. The X-rays are then transmitted through an object such as the body of a patient and are intercepted by a detector that forms an image of the object's internal anatomy.
The X-ray sources are typically high voltage sources. For example, an X-ray tube assembly typically operates with high voltage fed by high voltage cabling that pass through the housing to the cathode. Such high voltage operation severely limits the design aspects of the X-ray source assembly because it requires the high voltage to be insulated from other components of the X-ray source assembly. A high voltage insulator is required to protect certain components from the high voltages within the X-ray source assembly. The high voltage insulator is typically bulky, expensive, and decreases reliability of the X-ray source.
In a typical CT imaging apparatus, an X-ray tube and an X-ray detector rotate on a gantry at very high speeds around a patient located on a table at the center of the gantry. Faster rotation speeds are desirable for certain imaging applications. For example, imaging the heart may require an image to be obtained between heartbeats. However, increased rotation speeds create increased forces potentially limiting the X-ray tube's operation or reliability.
By contrast, in a stationary CT imaging apparatus, the X-ray source is a stationary arc source with distributed focal spots that can be activated by a control unit. The X-ray source includes a high voltage insulator to protect certain components within the X-ray source from the high operating voltage of up to 150 kV or larger. As mentioned above, the insulator must be large which causes cost, space, weight, reliability, and high voltage stability concerns.
Therefore, there is a need for reducing the cost, size and complexity of X-ray sources, and providing an X-ray source that does not require high voltage insulation.